Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/27

. I. nectary is shown only in the side view (n, fig. A); for its enlarged orifice is almost hidden in shade in the front view (B). The stigma (s) is bilobed, and consists of two almost confluent stigmas; it lies under the pouch-formed rostellum (r). The anther (a, in B and A) consists of two rather widely separated cells, which are longitudinally open in front: each cell includes a pollen-mass or pollinium.

A pollinium removed out of one of the two anther-cells is represented by fig. C; it consists of a number of wedge-formed packets of pollen-grains (see fig. F, in which the packets are forcibly separated), united together by excessively elastic, thin threads. These threads become confluent at the lower end of each pollen-mass, and compose the straight elastic caudicle (c, C). The end of the caudicle is firmly attached to the viscid disc (d, C), which consists (as may be seen in the section of the pouch-formed rostellum, fig. E) of a minute oval piece of membrane, with a ball of viscid matter on its under side. Each pollinium has its separate disc; and the two balls of viscid matter lie enclosed together (fig. D) within the rostellum.

The rostellum is a nearly spherical, somewhat pointed projection (r, figs. A and B) overhanging the two almost confluent stigmas, and must be fully described, as every detail of its structure is full of significance. A section through one of the discs and balls of viscid matter is given (fig. E); and a front view of both viscid dicsdiscs [sic] within the rostellum (fig. D) is likewise given. This latter figure (D) probably best serves to explain the structure of the rostellum; but it must be understood that the front lip is here considerably depressed. The lowest part of the anther is united to the back of the rostellum, as may be seen in fig. B. At an early period of growth the rostellum